The present invention relates to a permanent magnet rotating electrical machine, and relates to a permanent magnet rotating electrical machine suitable to wind power generation for example.
In recent years, the introduction quantity of the wind power generation has been increasing dramatically, and, aiming improvement of economic efficiency and improvement of efficiency of the generator by increasing the capacity of one machine as well as reduction of the size and weight, a demand for a permanent magnet rotating electrical machine having a large capacity of 1 MW or more is increasing.
In applying the permanent magnet rotating electrical machine having a large capacity, even if the efficiency may be high, the loss thereof becomes large as an absolute value. Therefore, when the heat generation density is to be made nearly equal to that of a small capacity machine to reduce the loss, the size of the permanent magnet rotating electrical machine has to be necessarily enlarged. When the size of the permanent magnet rotating electrical machine is enlarged, the weight increases, the cost increases, therefore the construction cost of the windmill increases, and therefore it is necessary to reduce the size of the permanent magnet rotating electrical machine and to increase the heat generation density.
In order to achieve a rotating electrical machine with a high heat generation density, it is necessary to strengthen the cooling construction. Although to arrange a duct is considered to be one of the solution in a rotating electrical machine that does not use ordinary permanent magnets, examples of arranging a duct in a permanent magnet rotating electrical machine having a large capacity are quite rare until now.
Therefore, when a duct is to be arranged in a rotor of a permanent magnet rotating electrical machine, particularly in a multi-pole machine with several tens poles or more, the circumferential dimension of the rotor per one pole becomes small, and therefore there is a problem that the permanent magnet and the duct interfere with each other in inserting the permanent magnet and assembling of the rotating electrical machine becomes impossible.
In JP-A-2012-39775, a technology has been disclosed in which the leakage magnetic flux is reduced by enlarging the shape of the magnet insertion hole into an arc shape in a permanent magnet rotating electrical machine having an air duct.